Exchange-coupled film, magnetoresistive element including the same, and magnetic sensing device

ABSTRACT

An exchange-coupled film includes an antiferromagnetic layer, pinned magnetic layer, and free magnetic layer which are stacked. The antiferromagnetic layer is composed of a Pt—Cr sublayer and an X—Mn sublayer (where X is Pt or Ir). The X—Mn sublayer is in contact with the pinned magnetic layer.

CLAIM OF PRIORITY

This application is a Continuation of International Application No.PCT/JP2017/009172 filed on Mar. 8, 2017, which claims benefit ofJapanese Patent Application No. 2016-157441 filed on Aug. 10, 2016. Theentire contents of each application noted above are hereby incorporatedby reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an exchange-coupled film, amagnetoresistive element including the same, and a magnetic sensingdevice.

2. Description of the Related Art

Exchange-coupled films including an antiferromagnetic layer and a pinnedmagnetic layer are used as magnetoresistive elements or magnetic sensingdevices. Japanese Unexamined Patent Application Publication No.2000-215431 (hereinafter referred to as the patent document) describesthat in a magnetic recording medium, an exchange-coupled film can beconfigured by combining a Co alloy serving as a ferromagnetic film withvarious alloys serving as antiferromagnetic films. As antiferromagneticfilms, alloys such as Co—Mn, Ni—Mn, Pt—Mn, and Pt—Cr are exemplified.

A magnetic sensing device requires solder reflowing (melting) when amagnetoresistive element is mounted on a board. The magnetic sensingdevice is used in a high-temperature environment such as the vicinity ofan engine in some cases. Therefore, an exchange-coupled film for use inthe magnetic sensing device preferably exhibits such a high magneticfield (Hex) that the magnetization direction of a pinned magnetic layeris reversed and also exhibits high stability under high-temperatureconditions for the purpose of enabling a magnetic field to be detectedin a wide dynamic range.

The patent document relates to an exchange-coupled film used as amagnetic recording medium and therefore does not describe the stabilityof a magnetic sensing device including an exchange-coupled film underhigh-temperature conditions. Although the patent document exemplifiesPt—Cr as an antiferromagnetic film, the patent document does notdescribe that composing Pt—Cr at what composition ratio is preferable.

SUMMARY OF THE INVENTION

The present invention provides an exchange-coupled film which exhibitssuch a high magnetic field (Hex) that the magnetization direction of apinned magnetic layer is reversed and which exhibits high stabilityunder high-temperature conditions, a magnetoresistive element includingthe same, and a magnetic sensing device.

An exchange-coupled film according to the present invention includes anantiferromagnetic layer and pinned magnetic layer which are stacked. Theantiferromagnetic layer is composed of a Pt—Cr sublayer and X—Mnsublayer (where, X is Pt or Ir). The X—Mn sublayer is in contact withthe pinned magnetic layer.

The pinned magnetic layer may be a self-pinned layer including a firstmagnetic sublayer, intermediate sublayer, and second magnetic sublayerwhich are stacked.

The thickness of the Pt—Cr sublayer is preferably greater than thethickness of the X—Mn sublayer.

The ratio of the thickness of the Pt—Cr sublayer to the thickness of theX—Mn sublayer is preferably 5:1 to 100:1.

The Pt—Cr sublayer preferably has a composition represented by theformula Pt_(X)Cr_(100 at %-X) (X is 45 at % to 62 at %) and morepreferably a composition represented by the formulaPt_(X)Cr_(100 at %-x) (X is 50 at % to 57 at %).

The exchange-coupled film preferably includes a base layer next to theantiferromagnetic layer. The base layer is preferably made of Ni—Fe—Cr.

A magnetoresistive element according to the present invention includesthe exchange-coupled film according to the present invention and a freemagnetic layer, the exchange-coupled film and the free magnetic layerbeing stacked.

A magnetic sensing device according to the present invention includesthe magnetoresistive element according to the present invention.

The magnetic sensing device according the present invention includes aplurality of magnetoresistive elements, placed on a single substrate,identical to the magnetoresistive element according to the presentinvention. The magnetoresistive elements include those having differentpinned magnetization directions.

A method for manufacturing an exchange-coupled film according to thepresent invention includes forming a Pt—Cr sublayer by a process forco-sputtering Pt and Cr.

An exchange-coupled film according to the present invention includes anantiferromagnetic layer composed of a Pt—Cr sublayer and an X—Mnsublayer (where X is Pt or Ir) and therefore exhibits such a highmagnetic field (Hex) that the magnetization direction of a pinnedmagnetic layer is reversed is high and increased stability underhigh-temperature conditions. Thus, using the exchange-coupled filmaccording to the present invention enables a magnetic sensing devicewhich is stable even if the magnetic sensing device is reflowed at hightemperature or is used in a high-temperature environment to be obtained.

In accordance with a manufacturing method according to the presentinvention, an exchange-coupled film including a pinned magnetic layerwith high Hex can be manufactured by co-sputtering Pt and Cr.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration showing the film configuration of anexchange-coupled film according to a first embodiment of the presentinvention;

FIG. 2 is an illustration showing the film configuration of anexchange-coupled film according to a second embodiment of the presentinvention;

FIG. 3 is a circuit block diagram of a magnetic sensor according to anembodiment of the present invention;

FIG. 4 is a plan view showing magnetic sensing elements 11 used in themagnetic sensor;

FIG. 5 is a graph showing R—H curves of a magnetic sensing elementprepared in Example 1;

FIG. 6 is a graph showing R—H curves of a magnetic sensing elementprepared in Example 2;

FIG. 7 is a graph showing R—H curves of a magnetic sensing elementprepared in Comparative Example 1;

FIG. 8 is a graph showing the Hex of each of exchange-coupled filmsprepared in Examples 3 to 5;

FIG. 9 is a graph showing the Hex of each of exchange-coupled filmsprepared in Example 6;

FIGS. 10A to 10C are graphs showing R—H curves of a magnetic sensingelement prepared in Example 7;

FIGS. 11A to 11C are graphs showing R—H curves of a magnetic sensingelement prepared in Example 8;

FIGS. 12A to 12C are graphs showing R—H curves of a magnetic sensingelement prepared in Comparative Example 2;

FIG. 13 is a graph showing the relationship between the percentage of Ptcontained in Pt—Cr prepared in each of Reference Example 1 and ReferenceExample 2 and the Hex;

FIG. 14 is a graph showing the relationship between the percentage of Ptcontained in Pt—Cr prepared in each of Reference Example 1 and ReferenceExample 3 and the Hex;

FIG. 15 is an illustration showing the film configuration of anexchange-coupled film prepared in each of Examples 9 to 12 andComparative Examples 3 and 4; and

FIG. 16 is a graph showing the relationship between the temperature ofan exchange-coupled film prepared in each of Examples 9 to 12 andComparative Examples 3 and 4 and the Hex.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

FIG. 1 shows the film configuration of a magnetic sensing element 11including an exchange-coupled film 10 according to a first embodiment ofthe present invention.

The magnetic sensing element 11 is formed by stacking a base layer 1, anantiferromagnetic layer 2, a pinned magnetic layer 3, an nonmagneticmaterial layer 4, a free magnetic layer 5, and a protective layer 6 inthat order from a surface of a substrate. The antiferromagnetic layer 2is composed of a Pt—Cr sublayer 2A and an X—Mn sublayer 2B (where, X isPt or Ir). The X—Mn sublayer 2B is in contact with the pinned magneticlayer 3. These layers are formed by, for example, a sputtering processor a CVD process. The base layer 1 and the pinned magnetic layer 3 formthe exchange-coupled film 10.

The magnetic sensing element 11 is a multilayer element using aso-called single spin valve type of giant magnetoresistive effect (GMReffect) and the electrical resistance thereof varies depending on therelative relation between the vector of the pinned magnetization of thepinned magnetic layer 3 and the vector of magnetization that variesdepending on the external magnetic field of the free magnetic layer 5.

The base layer 1 is formed from a Ni—Fe—Cr alloy (nickel-iron-chromiumalloy), Cr, Ta, or the like. In the exchange-coupled film 10, theNi—Fe—Cr alloy is preferable for the purpose of increasing the magneticfield (hereinafter also appropriately referred to as the “Hex”) at whichthe magnetization of the pinned magnetic layer 3 is reversed.

The antiferromagnetic layer 2 has a multilayer structure composed of thePt—Cr sublayer 2A and the X—Mn sublayer 2B (where, X is Pt or Ir). Inorder to increase the Hex, the thickness D1 of the Pt—Cr sublayer 2A ispreferably greater than the thickness D2 of the X—Mn sublayer 2B. Theratio of the thickness D1 to the thickness D2 (D1:D2) is preferably 5:1to 100:1 and more preferably 10:1 to 50:1.

From the viewpoint of increasing the Hex, the Pt—Cr sublayer 2Apreferably has a composition represented by the formulaPt_(X)Cr_(100 at %-X) (X is 45 at % to 62 at %) and more preferably acomposition represented by the formula Pt_(X)Cr_(100 at %-X) (X is 50 at% to 57 at %). From the same viewpoint, the X—Mn sublayer 2B ispreferably a Pt—Mn sublayer.

In this embodiment, the antiferromagnetic layer 2 is regularized byannealing, whereby exchange coupling is induced between (at theinterface between) the antiferromagnetic layer 2 and the pinned magneticlayer 3. The exchange coupling increases the strong-magnetic fieldresistance of the pinned magnetic layer 3 to increase the Hex.

The pinned magnetic layer 3 is formed from a Co—Fe alloy (cobalt-ironalloy). Increasing the content of Fe in the Co—Fe alloy increases thecoercive force thereof. The pinned magnetic layer 3 is a layercontributing to the spin valve type of giant magnetoresistive effect. Adirection in which the pinned magnetization direction P of the pinnedmagnetic layer 3 extends is the sensitivity axis direction of themagnetic sensing element 11.

The nonmagnetic material layer 4 can be formed using Cu (copper) or thelike.

The free magnetic layer 5 is not limited in material or structure. Thefree magnetic layer 5 can be formed using, for example, material such asa Co—Fe alloy (cobalt-iron alloy) or a Ni—Fe alloy (nickel-iron alloy)in the form of a single-layer structure, a multilayer structure, or amultilayered ferrimagnetic structure.

The protective layer 6 can be formed using Ta (tantalum).

Second Embodiment

FIG. 2 is an illustration showing the film configuration of a magneticsensing element 21 including an exchange-coupled film 20 according to asecond embodiment of the present invention. In this embodiment, layershaving the same function as that of the magnetic sensing element 11shown in FIG. 1 are given the same reference numerals and will not bedescribed in detail.

In the magnetic sensing element 21, the exchange-coupled film 20 iscomposed of a pinned magnetic layer 3 with a self-pinned structure andan antiferromagnetic layer 2 joined thereto. The magnetic sensingelement 21 differs from the magnetic sensing element 11 shown in FIG. 1in that a nonmagnetic material layer 4 and a free magnetic layer 5 areplaced under the pinned magnetic layer 3.

The magnetic sensing element 21 is also a multilayer element using aso-called single spin valve type of giant magnetoresistive effect. Theelectrical resistance thereof varies depending on the relative relationbetween the vector of the pinned magnetization of a first magneticsublayer 3A of the pinned magnetic layer 3 and the vector ofmagnetization that varies depending on the external magnetic field ofthe free magnetic layer 5.

The pinned magnetic layer 3 has a self-pinned structure composed of thefirst magnetic sublayer 3A, a second magnetic sublayer 3C, and anonmagnetic intermediate sublayer 3B located between these twosublayers. The pinned magnetization direction P1 of the first magneticsublayer 3A is antiparallel to the pinned magnetization direction P2 ofthe second magnetic sublayer 3C because of interaction. The firstmagnetic sublayer 3A is next to the nonmagnetic material layer 4 and thepinned magnetization direction P1 of the first magnetic sublayer 3A isthe pinned magnetization direction of the pinned magnetic layer 3. Adirection in which the pinned magnetization direction P1 extends is thesensitivity axis direction of the magnetic sensing element 21.

The first magnetic sublayer 3A and the second magnetic sublayer 3C areformed from an Fe—Co alloy (iron-cobalt alloy). Increasing the contentof Fe in the Fe—Co alloy increases the coercive force thereof. The firstmagnetic sublayer 3A, which is next to the nonmagnetic material layer 4,is a layer contributing to the spin valve type of giant magnetoresistiveeffect.

The nonmagnetic intermediate sublayer 3B is formed from Ru (ruthenium)or the like. The nonmagnetic intermediate sublayer 3B, which is made ofRu, preferably has a thickness of 3 Å to 5 Å or 8 Å to 10 Å.

Configuration of Magnetic Sensor

FIG. 3 shows a magnetic sensor (magnetic sensing device) 30 including aplurality of magnetic sensing elements identical to the magnetic sensingelement 11 shown in FIG. 1.

Referring to FIG. 3, the magnetic sensing elements are different inpinned magnetization direction P (refer to FIG. 1) and are givendifferent reference numerals 11Xa, 11Xb, 11Ya, and 11Yb fordiscrimination purposes. In the magnetic sensor 30, the magnetic sensingelements 11Xa, 11Xb, 11Ya, and 11Yb are placed on a single substrate.

As shown in FIG. 3, the magnetic sensor 30 includes a full bridgecircuit 32X and a full bridge circuit 32Y. The full bridge circuit 32Xincludes the two magnetic sensing elements 11Xa and the two magneticsensing elements 11Xb. The full bridge circuit 32Y includes the twomagnetic sensing elements 11Ya and two magnetic sensing elements 11Yb.The magnetic sensing elements 11Xa, 11Xb, 11Ya, and 11Yb have the filmstructure of the exchange-coupled film 10 of the magnetic sensingelement 11 shown in FIG. 1. These are hereinafter appropriately referredto as the magnetic sensing elements 11 unless these are discriminated.

The full bridge circuit 32X and the full bridge circuit 32Y include themagnetic sensing elements 11 having different pinned magnetizationdirections indicated by arrows as shown in FIG. 3 for the purpose ofallowing detected magnetic field directions to differ and have the samemechanism for detecting a magnetic field. A mechanism for detecting amagnetic field using the full bridge circuit 32X is described below.

The full bridge circuit 32X is composed of a first series section 32Xaand second series section 32Xb connected in series to each other. Thefirst series section 32Xa is composed of the magnetic sensing elements11Xa and 11Xb connected in series to each other. The second seriessection 32Xb is composed of the magnetic sensing elements 11Xb and 11Xaconnected in series to each other.

A power-supply voltage Vdd is applied to a power-supply terminal 33common to the magnetic sensing element 11Xa included in the first seriessection 32Xa and the magnetic sensing element 11Xb included in thesecond series section 32Xb. A ground terminal 34 common to the magneticsensing element 11Xb included in the first series section 32Xa and themagnetic sensing element 11Xa included in the second series section 32Xbis set to the ground potential GND.

The differential output (OutX1)−(OutX2) between the output potential(OutX1) of the midpoint 35Xa of the first series section 32Xa and theoutput potential (OutX2) of the midpoint 35Xb of the second seriessection 32Xb is obtained as a detection output (detection outputvoltage) VXs in an X-direction.

The full bridge circuit 32Y works similarly to the full bridge circuit32X and therefore the differential output (OutY1)−(OutY2) between theoutput potential (OutY1) of the midpoint 35Ya of a first series section32Ya included in the full bridge circuit 32Y and the output potential(OutY2) of the midpoint 35Yb of a second series section 32Yb included inthe full bridge circuit 32Y is obtained as a detection output (detectionoutput voltage) VYs in a Y-direction.

As indicated by arrows in FIG. 3, the sensitivity axis direction of eachof the magnetic sensing elements 11Xa and 11Xb forming the full bridgecircuit 32X is perpendicular to the sensitivity axis direction of eachof the magnetic sensing elements 11Ya and 11Yb forming the full bridgecircuit 32Y.

As shown in FIG. 3, in the magnetic sensor 30, the orientation of thefree magnetic layer 5 of each magnetic sensing element 11 varies so asto follow the direction of an external magnetic field H. In this event,the resistance varies depending on the vector relationship between thepinned magnetization direction P of the pinned magnetic layer 3 and themagnetization direction of the free magnetic layer 5.

Supposing that, for example, the external magnetic field H acts in adirection shown in FIG. 3. The magnetic sensing element 11Xa included inthe full bridge circuit 32X exhibits a reduced electrical resistancebecause the sensitivity axis direction coincides with the direction ofthe external magnetic field H. However, the magnetic sensing element11Xb exhibits an increased electrical resistance because the sensitivityaxis direction is opposite to the direction of the external magneticfield H. The change of the electrical resistance allows the detectionoutput voltage VXs=(OutX1)−(OutX2) to peak. As the external magneticfield H changes rightward with respect to the plane of FIG. 3, thedetection output voltage VXs decreases. As the external magnetic field Hchanges upward or downward with respect to the plane of FIG. 3, thedetection output voltage VXs decreases to zero.

On the other hand, in the full bridge circuit 32Y, when the externalmagnetic field H is leftward with respect to the plane of FIG. 3, themagnetization direction of the free magnetic layer 5 of every magneticsensing element 11 is perpendicular to the sensitivity axis direction(pinned magnetization direction P) and therefore the magnetic sensingelements 11Ya and 11Xb exhibit the same resistance. Thus, the detectionoutput voltage VYs is zero. When the external magnetic field H actsdownward with respect to the plane of FIG. 3, the detection outputvoltage VYs=(OutY1)−(OutY2) of the full bridge circuit 32Y peaks. As theexternal magnetic field H changes upward with respect to the planethereof, the detection output voltage VYs decreases.

As described above, as the direction of the external magnetic field Hchanges, the detection output voltage VXs of the full bridge circuit 32Xand the detection output voltage VYs of the full bridge circuit 32Yvary. Thus, the movement direction and travel distance (relativeposition) of a detection target can be detected on the basis of thedetection output voltages VXs and VYs obtained from the full bridgecircuits 32X and 32Y.

FIG. 3 shows the magnetic sensor 30, which is configured to be capableof detecting a magnetic field in the X-direction and a Y-directionperpendicular to the X-direction. However, the magnetic sensor 30 may beconfigured to include the full bridge circuit 32X or the full bridgecircuit 32Y only so as to detect a magnetic field in the X-direction orthe Y-direction, respectively, only.

FIG. 4 shows the planar structure of each of the magnetic sensingelements 11Xa and 11Xb. In FIGS. 3 and 4, a BXa-BXb direction is theX-direction. In FIG. 4, (A) and (B) show the pinned magnetizationdirections P of the magnetic sensing elements 11Xa and 11Xb as indicatedby arrows. The pinned magnetization directions P of the magnetic sensingelements 11Xa and 11Xb are the X-direction and are opposite to eachother.

As shown in FIG. 4, the magnetic sensing elements 11Xa and 11Xb eachinclude stripe-shaped element sections 12. The longitudinal direction ofeach element section 12 is directed in a BYa-BYb direction. A pluralityof the element sections 12 are placed in parallel to each other.Illustrated right end portions of the neighboring element sections 12are connected to each other with conductive sections 13 a. Illustratedleft end portions of the neighboring element sections 12 are connectedto each other with conductive sections 13 b. The conductive sections 13a and 13 b are alternately connected to the illustrated right and leftend portions of the element sections 12, whereby the element sections 12are coupled to each other in a so-called meander pattern. In themagnetic sensing elements 11Xa and 11Xb, the conductive section 13 ashown in a lower right portion is united with a connection terminal 14 aand the conductive section 13 b shown in an upper left portion is unitedwith a connection terminal 14 b.

Each element section 12 is composed of a plurality of stacked metallayers (alloy layers). FIG. 1 shows the multilayer structure of theelement section 12. The element section 12 may have a multilayerstructure shown in FIG. 2.

In the magnetic sensor 30 shown in FIGS. 3 and 4, the magnetic sensingelement 11 can be replaced with the magnetic sensing element 21, shownin FIG. 2, according to the second embodiment.

EXAMPLES Example 1

A magnetic sensing element 11 (refer to FIG. 1) including anexchange-coupled film 10 having a film configuration below was prepared.In examples, comparative examples, and reference examples below, aparenthesized value is a thickness (Å). The exchange-coupled film 10 wasannealed at 400° C. for 5 hours in a magnetic field of 1 kOe, wherebythe magnetization of each of a pinned magnetic layer 3 and anantiferromagnetic layer 2 was pinned.

Substrate/base layer 1: Ni—Fe—Cr (60)/antiferromagnetic layer 2 [Pt—Crsublayer 2A: Pt_(51 at %)-Cr_(49 at %) (280)/X—Mn sublayer 2B:Pt_(50 at %)-Mn_(50 at %) (20)]/pinned magnetic layer 3:Co_(90 at %)-Fe_(10 at %) (50)/nonmagnetic material layer 4: Cu(40)/free magnetic layer 5: Co_(90 at %)-Fe_(10 at %)(15)/Ni_(81.5 at %)-Fe_(18.5 at %) (30)/protective layer 6: Ta (50)

Example 2

A magnetic sensing element 11 including an exchange-coupled film 10having a film configuration below was prepared by changing a Pt—Crsublayer 2A of an antiferromagnetic layer 2 fromPt_(51 at %)-Cr_(49 at %) (280) prepared in Example 1 toPt_(54 at %)-Cr_(46 at %) (280).

Substrate/base layer 1: Ni—Fe—Cr (60)/antiferromagnetic layer 2 [Pt—Crsublayer 2A: Pt_(54 at %)-Cr_(46 at %) (280)/X—Mn sublayer 2B:Pt_(50 at %)-Mn_(50 at %) (20)]/pinned magnetic layer 3:Co_(90 at %)-Fe_(10 at %) (50)/nonmagnetic material layer 4: Cu(40)/free magnetic layer 5: Co_(90 at %)-Fe_(10 at %)(15)/Ni_(81.5 at %)-Fe_(18.5 at %) (30)/protective layer 6: Ta (50)

Comparative Example 1

A magnetic sensing element 11 including an exchange-coupled film 10having a film configuration below was prepared by changing anantiferromagnetic layer 2 from [Pt—Cr sublayer 2A:Pt_(51 at %)-Cr_(49 at %) (280)/X—Mn sublayer 2B:Pt_(50 at %)-Mn_(50 at %) (20)] prepared in Example 1 toPt_(50 at %)-Mn_(50 at %) (300).

Substrate/base layer 1: Ni—Fe—Cr (60)/antiferromagnetic layer 2:Pt_(50 at %)-Mn_(50 at %) (300)/pinned magnetic layer 3:Co_(90 at %)-Fe_(10 at %) (50)/nonmagnetic material layer 4: Cu(40)/free magnetic layer 5: Co_(90 at %)-Fe_(10 at %)(15)/Ni_(81.5 at %)-Fe_(18.5 at %) (30)/protective layer 6: Ta (50)

Application of External Magnetic Field

An external magnetic field H was applied to the magnetic sensing element11 prepared in each of Example 1, Example 2, and Comparative Example 1from a direction parallel to the pinned magnetization direction (aP-direction in FIG. 1) of the pinned magnetic layer 3 of theexchange-coupled film 10, whereby the rate (rate of change inresistance) ΔMR (ΔR/R) at which the electrical resistance R was changedby the magnetic field H was determined.

FIG. 5, FIG. 6, and FIG. 7 show R—H curves of the magnetic sensingelement 11 prepared in Example 1, R—H curves of the magnetic sensingelement 11 prepared in Example 2, and R—H curves of the magnetic sensingelement 11 prepared in Comparative Example 1, respectively. In each ofthese figures, the horizontal axis represents the intensity [Oe] of themagnetic field H, the vertical axis represents the rate of change inresistance ΔMR [%], a curve (a curve located on a lower side at H=1,000[Oe]) marked “Inc.” represents ΔMR in the case of increasing themagnetic field H, and a curve (a curve located on an upper side atH=1,000 [Oe]) marked “Dec.” represents ΔMR in the case of reducing themagnetic field H.

Referring to FIGS. 5 to 7, hysteresis appears in the variation curve“Inc.” of the rate of change in resistance ΔMR [o] in the case ofchanging the magnetic field to a positive side and the variation curve“Dec.” of the rate of change in resistance ΔMR [o] in the case ofchanging the magnetic field to a negative side and the median of thefull width at half maximum of each of the variation curve “Inc.” and thevariation curve “Dec.” substantially coincides with the magnetic field(Hex) at which the magnetization direction of a pinned magnetic layer isreversed.

It was clear that the magnetic sensing element 11 prepared in Example 1and the magnetic sensing element 11 prepared in Example 2 exhibited ahigher magnetic field (Hex) as compared to the magnetic sensing element11 prepared in Comparative Example 1. That is, the magnetic sensingelements 11 including the exchange-coupled films 10 prepared in Examples1 and 2 can sufficiently measure a magnetic field in a strong-magneticfield environment.

Example 3

Exchange-coupled films 10 (refer to FIG. 1) having a film configurationbelow were prepared by varying the thickness D1 of a Pt—Cr sublayer 2Aof an antiferromagnetic layer 2 and the thickness D2 of a Pt—Mn sublayer2B thereof. The exchange-coupled films 10 were annealed at 400° C. for 5hours in a magnetic field of 1 kOe, whereby the magnetization of each ofa pinned magnetic layer 3 and the antiferromagnetic layer 2 was pinned.

Substrate/base layer 1: Ni—Fe—Cr (60)/antiferromagnetic layer 2 [Pt—Crsublayer 2A: Pt_(54 at %)-Cr_(46 at %) (300−x)/X—Mn sublayer 2B:Pt_(50 at %)-Mn_(50 at %) (x)]/pinned magnetic layer 3:Co_(90 at %)-Fe_(10 at %) (50)/nonmagnetic material layer 4: Cu(40)/free magnetic layer 5: Co_(90 at %)-Fe_(10 at %)(15)/Ni_(81.5 at %)-Fe_(18.5 at %) (30)/protective layer 6: Ta (50)

For each exchange-coupled film 10 including the Pt—Cr sublayer 2A andPt—Mn sublayer having a thickness shown in Table 1, the Hex calculatedfrom an R—H curve was as described below. Hereinafter,Pt_(54 at %)-Cr_(46 at %) is appropriately referred to as 54Pt—Cr,Pt_(51 at %)-Cr_(49 at %) is appropriately referred to as 51Pt—Cr, andPt_(50 at %)-Mn_(50 at %) is appropriately referred to as Pt—Mn.

TABLE 1 Thickness of 54Pt—Cr Thickness of Pt—Mn sublayer sublayer Hex atroom temperature D1 [Å] (300 − x) D2 [Å] (x) Hex [Oe] 300 0 238 298 2364 296 4 519 294 6 634 292 8 790 290 10 917 288 12 1033 286 14 1149 28416 1263 282 18 1348 280 20 1430 278 22 1462 276 24 1463 274 26 1466 27228 1423 270 30 1372 266 34 1034 262 38 842 250 50 721 200 100 620 100200 724 0 300 590

Example 4

Exchange-coupled films 10 having a film configuration below wereprepared by changing a Pt—Cr sublayer 2A of an antiferromagnetic layer 2from 54Pt—Cr (280-x) prepared in Example 3 to 51Pt—Cr (280-x). Theexchange-coupled films 10 were annealed at 400° C. for 5 hours in amagnetic field of 1 kOe, whereby the magnetization of each of a pinnedmagnetic layer 3 and the antiferromagnetic layer 2 was pinned.

Substrate/base layer 1: Ni—Fe—Cr (60)/antiferromagnetic layer 2 [Pt—Crsublayer 2A: Pt_(51 at %)-Cr_(49 at %) (300-x)/X—Mn sublayer 2B:Pt_(50 at %)-Mn_(50 at %) (x)]/pinned magnetic layer 3:Co_(90 at %)-Fe_(10 at %) (50)/nonmagnetic material layer 4: Cu(40)/free magnetic layer 5: Co_(90 at %)-Fe_(10 at %)(15)/Ni_(81.5 at %)-Fe_(18.5 at %) (30)/protective layer 6: Ta (50)

For each exchange-coupled film 10 including the Pt—Cr sublayer 2A andPt—Mn sublayer having a thickness shown in Table 2, the Hex calculatedfrom an R—H curve was as described below.

TABLE 2 Thickness of 51Pt—Cr Thickness of Pt—Mn Hex at room temperaturesublayer D1 [Å] sublayer D2 [Å] Hex [Oe] 300 0 111 296 4 298 292 8 522288 12 717 284 16 893 280 20 1039 276 24 1141 272 28 1113 250 50 610 200100 523 100 200 663 0 300 590

Example 5

Exchange-coupled films 10 having the same film configuration as that ofExample 4 were prepared and the temperature of annealing was changedfrom 400° C. of Example 4 to 350° C.

For each exchange-coupled film 10 including a 51Pt—Cr sublayer and Pt—Mnsublayer having a thickness shown in Table 3, the Hex calculated from anR—H curve was as described below.

TABLE 3 Thickness of 51Pt—Cr Thickness of Pt—Mn Hex at room temperaturesublayer D1 [Å] sublayer D2 [Å] Hex [Oe] 300 0 210 296 4 407 292 8 709288 12 840 284 16 951 280 20 1056 276 24 1064 272 28 1131 250 50 740 200100 600 100 200 688 0 300 612

FIG. 8 is a graph showing the Hex of each of the exchange-coupled films10 prepared in Examples 3 to 5. In this figure, the horizontal axisrepresents the thickness of a Pt—Mn sublayer (Pt—Mn thickness, [Å]) andthe vertical axis represents the Hex [Oe] of an exchange-coupled film.As is clear from FIG. 8 and Tables 1 to 3, using either of 51Pt—Cr and54Pt—Cr as a Pt—Cr sublayer allows the exchange-coupled films 10 toexhibit a higher Hex as compared to those including an antiferromagneticlayer composed of a Pt—Mn sublayer only.

From the viewpoint of allowing an exchange-coupled film 10 to have ahigh Hex, 54Pt—Cr is preferably used as a Pt—Cr sublayer. Even if theannealing temperature is 350° C., an exchange-coupled film 10 havingsubstantially the same Hex as that at 400° C. is obtained. Therefore,from the viewpoint of reducing the annealing temperature, 51Pt—Cr ispreferably used as a Pt—Cr sublayer.

Example 6

Exchange-coupled films 10 having a film configuration below wereprepared by changing an X—Mn sublayer 2B of an antiferromagnetic layer 2from Pt—Mn prepared in Example 3 to Ir—Mn. The exchange-coupled films 10were annealed at 400° C. for 5 hours in a magnetic field of 1 kOe,whereby the magnetization of each of a pinned magnetic layer 3 and theantiferromagnetic layer 2 was pinned.

Substrate/base layer 1: Ni—Fe—Cr (60)/antiferromagnetic layer 2 [Pt—Crsublayer 2A: Pt_(54 at %)-Cr_(46 at %) (300-x)/X—Mn sublayer 2B:Ir_(50 at %)-Mn_(50 at %) (x)]/pinned magnetic layer 3:Co_(90 at %)-Fe_(10 at %) (50)/nonmagnetic material layer 4: Cu(40)/free magnetic layer 5: Co_(90 at %)-Fe_(10 at %)(15)/Ni_(81.5 at %)-Fe_(18.5 at %) (30)/protective layer 6: Ta (50)

For each exchange-coupled film 10 including a Pt—Cr sublayer and Ir—Mnsublayer having a thickness shown in Table 4, the Hex calculated from anR—H curve was as described below.

TABLE 4 Thickness of Pt—Cr Thickness of Ir—Mn Hex at room temperaturesublayer D1 [Å] sublayer D2 [Å] Hex [Oe] 300 0 238 298 2 283 296 4 293294 6 281 292 8 199 290 10 156 280 20 85 260 40 167 0 80 162

FIG. 9 is a graph showing the Hex of each of the exchange-coupled films10 prepared in Example 6. In this figure, the horizontal axis representsthe thickness of an Ir—Mn sublayer (Ir—Mn thickness [Å]) and thevertical axis represents the Hex [Oe] of an exchange-coupled film. As isclear from FIG. 9 and Table 4, the effect of increasing the Hex of aPt—Cr sublayer is provided by an antiferromagnetic layer combined withIr—Mn similarly to a Pt—Mn sublayer.

Example 7

A magnetic sensing element 21 (refer to FIG. 2) including anexchange-coupled film 20 having a film configuration below was prepared.A parenthesized value is a thickness (Å) The exchange-coupled film 20was annealed at 350° C. for 5 hours in no magnetic field and was therebystabilized.

Substrate/base layer 1: Ni—Fe—Cr (42)/free magnetic layer 5:Ni_(81.5 at %)-Fe_(18.5 at %) (18)/:Co_(90 at %)-Fe_(10 at %)(14)/nonmagnetic material layer 4: Cu (30)/pinned magnetic layer 3[first magnetic sublayer 3A: Co_(90 at %)-Fe_(10 at %) (24)/nonmagneticintermediate sublayer 3B: Ru (3.6)]/second magnetic sublayer 3C:Fe_(60 at %)-Co_(40 at %) (17)/antiferromagnetic layer 2 [X—Mn sublayer:Pt_(50 at %)-Mn_(50 at %) (20)/Pt_(51 at %)-Cr_(49 at %)(280)]/protective layer 6: Ta (90)

Example 8

A magnetic sensing element 21 including an exchange-coupled film 20having a film configuration below was prepared by changing anantiferromagnetic layer 2 from [X—Mn sublayer: Pt—Mn (20)/51Pt—Cr (280)]prepared in Example 7 to [X—Mn sublayer: Ir—Mn (4)/51Pt—Cr (296)].

Substrate/base layer 1: Ni—Fe—Cr (42)/free magnetic layer 5:Ni_(81.5 at %)-Fe_(18.5 at %) (18)/:Co_(90 at %)-Fe_(10 at %)(14)/nonmagnetic material layer 4: Cu (30)/pinned magnetic layer 3[first magnetic sublayer 3A: Co_(90 at %)-Fe_(10 at %) (24)/nonmagneticintermediate sublayer 3B: Ru (3.6)]/second magnetic sublayer 3C:Fe_(60 at %)-Co_(40 at %) (17)/antiferromagnetic layer 2 [X—Mn sublayer:Ir_(50 at %)-Mn_(50 at %) (4)/Pt_(51 at %)-Cr_(49 at %)(296)]/protective layer 6: Ta (90)

Comparative Example 2

A magnetic sensing element 21 including an exchange-coupled film 20having a film configuration below was prepared by changing anantiferromagnetic layer 2 from [X—Mn sublayer: Pt—Mn (20)/51Pt—Cr (280)]prepared in Example 7 to Pt—Mn (300).

Substrate/base layer 1: Ni—Fe—Cr (42)/free magnetic layer 5:Ni_(81.5 at %)-Fe_(18.5 at %) (18)/:Co_(90 at %)-Fe_(10 at %)(14)/nonmagnetic material layer 4: Cu (30)/pinned magnetic layer 3[first magnetic sublayer 3A: Co_(90 at %)-Fe_(10 at %) (24)/nonmagneticintermediate sublayer 3B: Ru (3.6)]/second magnetic sublayer 3C:Fe_(60 at %)-Co_(40 at %) (17)/antiferromagnetic layer 2:Pt_(50 at %)-Mn_(50 at %) (300)/protective layer 6: Ta (90)

Application of External Magnetic Field

An external magnetic field H was applied to the magnetic sensing element21 prepared in each of Example 7, Example 8, and Comparative Example 2from a direction parallel to the pinned magnetization direction (a P1direction in FIG. 2) of the pinned magnetic layer 3, whereby the rate ofchange in resistance ΔMR (ΔR/R) was determined.

FIGS. 10A to 10C, FIGS. 11A to 11C, and FIGS. 12A to 12C show R—H curvesof the magnetic sensing element 21 prepared in Example 7, R—H curves ofthe magnetic sensing element 21 prepared in Example 8, and R—H curves ofthe magnetic sensing element 21 prepared in Comparative Example 2,respectively. In each of these figures, the horizontal axis representsthe intensity [Oe] of the magnetic field H, the vertical axis representsΔMR (%), a curve marked “Inc.” represents ΔMR in the case of increasingthe magnetic field H, and a curve marked “Dec.” represents ΔMR in thecase of reducing the magnetic field H.

FIGS. 10A to 10C and FIGS. 11A to 11C show less hysteresis as comparedto FIGS. 12A to 12C and show an improvement in a ΔMR reduction processdown to +5 kOe. This result shows that an antiferromagnetic layer whichis composed of a Pt—Cr sublayer and a Pt—Mn sublayer and in which thePt—Mn sublayer is in contact with a pinned magnetic layer enhances thestabilization of an exchange-coupled film even when the pinned magneticlayer is a self-pinned layer including a first magnetic sublayer,intermediate sublayer, and second magnetic sublayer which are stacked.

Reference Example 1

Magnetic sensing elements having a film configuration below wereprepared. A parenthesized value is a thickness (Å). Eachexchange-coupled film 10 was annealed at 400° C. for 5 hours in amagnetic field of 1 kOe, whereby the magnetization of each of a pinnedmagnetic layer 3 and an antiferromagnetic layer 2 were pinned.

Substrate/base layer 1: Ni—Fe—Cr (60)/antiferromagnetic layer 2:Pt_(X)Cr_(100 at %-X) (300)/pinned magnetic layer 3:Co_(90 at %)-Fe_(10 at %) (50)/nonmagnetic material layer 4: Cu(40)/free magnetic layer 5: [Co_(90 at %)-Fe_(10 at %) (15)/81.5Ni—Fe(30)]/protective layer 6: Ta (50)

By co-sputtering Pt and Cr, Pt_(X)Cr_(100 at %-X) (300) films havingdifferent Pt-to-Cr ratios were prepared.

Reference Example 2

Pt_(X)Cr_(100 at %-X) (300) films having different Pt-to-Cr ratios wereprepared in substantially the same manner as that used in ReferenceExample 1 except that Pt and Cr were alternately stacked instead ofco-sputtering Pt and Cr.

Reference Example 3

Pt_(X)Cr_(100 at %-X) (300) films having different Pt-to-Cr ratios wereprepared in substantially the same manner as that used in Example 1except that a base layer 1 was changed from Ni—Fe—Cr (60) prepared inExample 1 to Ta (50).

Sputtering and Alternate Stacking

FIG. 13 is a graph showing the relationship between the percentage of Ptcontained in Pt—Cr prepared in each of Reference Example 1(co-sputtering) and Reference Example 2 (alternate stacking) and theHex. As is clear from this figure, Reference Example 1, in whichPt_(X)Cr_(100 at %-X) films were formed by co-sputtering, provides ahigher Hex as compared to Reference Example 2, in whichPt_(X)Cr_(100 at %-X) films were formed by alternate stacking, withinthe Pt percentage range of 51 at % to 57 at %.

Base Layer

FIG. 14 is a graph showing the relationship between the percentage of Ptcontained in Pt—Cr prepared in each of Reference Example 1 and ReferenceExample 3 and the Hex. As is clear from this figure, exchange-coupledfilms Reference Example 1 (Ni—Fe—Cr base) exhibits a significantlyhigher Hex as compared to Reference Example 3 (Ta base) within the Ptpercentage range of 51 at % to 57 at %.

Example 9

In order to investigate the relationship between the temperature and theHex, an exchange-coupled film 40 having a structure shown in FIG. 15 wasprepared.

Substrate/base layer 1: Ni—Fe—Cr (42)/antiferromagnetic layer 2/pinnedmagnetic layer 3: 90Co—Fe (100)/protective layer 6: Ta (90)

The exchange-coupled film 40 was formed by setting an antiferromagneticlayer 2 to 51Pt—Cr (280)/Pt—Mn (20) and was annealed at 350° C. for 5hours in a magnetic field of 1 kOe such that the magnetization of eachof a pinned magnetic layer 3 and the antiferromagnetic layer 2 waspinned.

Comparative Example 3

An exchange-coupled film 40 was formed by setting an antiferromagneticlayer 2 to 51Pt—Cr (300) and was annealed at 350° C. for 5 hours in amagnetic field of 1 kOe such that the magnetization of each of a pinnedmagnetic layer 3 and the antiferromagnetic layer 2 was pinned.

Table 5 shows results obtained by measuring the exchange-coupled film 40prepared in each of Example 9 and Comparative Example 3 for a change inHex due to a change in temperature. In Tables 5 to 7, Tb represents thetemperature at which the Hex vanishes and Hex (200° C. or 300° C.)/Hex(room temperature) represents a normalized value obtained by dividingthe Hex at 200° C. or 300° C. by the Hex at room temperature.

TABLE 5 Thickness of Thickness 51Pt—Cr of Pt—Mn Hex (200° C.)/ Hex (300°C.)/ sublayer sublayer Tb Hex (room Hex (room D1 [Å] D2 [Å] (° C.)temperature) temperature) 300 0 460 0.96 0.66 280 20 >500 0.88 0.75

Example 10

An exchange-coupled film 40 was formed by setting an antiferromagneticlayer 2 to 51Pt—Cr (280)/Pt—Mn (20) and was annealed at 400° C. for 5hours in a magnetic field of 1 kOe such that the magnetization of eachof a pinned magnetic layer 3 and the antiferromagnetic layer 2 waspinned.

Comparative Example 4

An exchange-coupled film 40 was formed by setting an antiferromagneticlayer 2 to Pt—Mn (300) and was annealed at 400° C. for 5 hours in amagnetic field of 1 kOe such that the magnetization of each of a pinnedmagnetic layer 3 and the antiferromagnetic layer 2 was pinned.

Table 6 shows measurement result of Example 10 and Comparative Example4.

TABLE 6 Thickness Thickness of of Pt—Mn Hex (200° C.)/ Hex (300° C.)/51Pt—Cr sublayer sublayer Tb Hex (room Hex (room D1 [Å] D2 [Å] (° C.)temperature) temperature) 280 20 >500 0.86 0.76 0 300 400 0.82 0.35

Example 11

An exchange-coupled film 40 was formed by setting an antiferromagneticlayer 2 to 54Pt—Cr (290)/Pt—Mn (10) and was annealed at 400° C. for 5hours in a magnetic field of 1 kOe such that the magnetization of eachof a pinned magnetic layer 3 and the antiferromagnetic layer 2 waspinned.

Example 12

An exchange-coupled film 40 was formed by setting an antiferromagneticlayer 2 to 54Pt—Cr (280)/Pt—Mn (20) and was annealed at 400° C. for 5hours in a magnetic field of 1 kOe such that the magnetization of eachof a pinned magnetic layer 3 and the antiferromagnetic layer 2 waspinned.

Table 7 shows measurement result of Examples 11 and 12 and ComparativeExample 4.

TABLE 7 Thickness Thickness of of Pt—Mn Hex (200° C.)/ Hex (300° C.)/54Pt—Cr sublayer sublayer Tb Hex (room Hex (room D1 [Å] D2 [Å] (° C.)temperature) temperature) 290 10 500 0.98 0.86 280 20 >500 0.91 0.80 0300 400 0.82 0.35

FIG. 16 is a graph showing the relationship between the temperature ofthe exchange-coupled film 40 prepared in each of Examples 9 to 12 andComparative Examples 3 and 4 and the Hex. This graph shows resultsobtained by measuring the quantity corresponding to the Hex in the R—Hcurve of each of FIGS. 5 to 7 using a VSM (vibrating samplemagnetometer).

As shown in FIG. 16 and Tables 5 to 7, an exchange-coupled film 40including an antiferromagnetic layer 2 including a Pt—Mn sublayer and aPt—Cr sublayer inserted therein exhibited higher Tb as compared to anexchange-coupled film including an antiferromagnetic layer 2 made ofPt—Mn only and also exhibited high stability under high-temperatureconditions for maintaining high Hex.

1. An exchange-coupled film comprising an antiferromagnetic layercomposed of a Pt—Cr sublayer and an X—Mn sublayer (where X is Pt or Ir);and a pinned magnetic layer, the antiferromagnetic layer and the pinnedmagnetic layer being stacked, wherein the X—Mn sublayer of theantiferromagnetic layer is in contact with the pinned magnetic layer. 2.The exchange-coupled film according to claim 1, wherein the pinnedmagnetic layer is a self-pinned layer including a first magneticsublayer, intermediate sublayer, and second magnetic sublayer which arestacked.
 3. The exchange-coupled film according to claim 1, wherein thethickness of the Pt—Cr sublayer is greater than the thickness of theX—Mn sublayer.
 4. The exchange-coupled film according to claim 3,wherein the ratio of the thickness of the Pt—Cr sublayer to thethickness of the X—Mn sublayer is 5:1 to 100:1.
 5. The exchange-coupledfilm according to claim 1, wherein the Pt—Cr sublayer has a compositionrepresented by the formula Pt_(X)Cr_(100 at %-X) (X is 45 at % to 62 at%).
 6. The exchange-coupled film according to claim 1, wherein the Pt—Crsublayer has a composition represented by the formulaPt_(X)Cr_(100 at %-X) (X is 50 at % to 57 at %).
 7. The exchange-coupledfilm according to claim 1, further comprising a base layer next to theantiferromagnetic layer, wherein the base layer is made of Ni—Fe—Cr. 8.A magnetoresistive element comprising the exchange-coupled filmaccording to claim 1 and a free magnetic layer, the exchange-coupledfilm and the free magnetic layer being stacked.
 9. A magnetic sensingdevice comprising the magnetoresistive element according to claim
 8. 10.The magnetic sensing device according to claim 9, further comprising aplurality of magnetoresistive elements, placed on a single substrate,identical to the magnetoresistive element according to claim 8, whereinthe magnetoresistive elements include those having different pinnedmagnetization directions.
 11. A method for manufacturing theexchange-coupled film according to claim 1, comprising forming the Pt—Crsublayer by a process for co-sputtering Pt and Cr.